The matrix metallo proteases (MMPs) are a large family of enzymes that have been found to regulate the pathogenesis of a wide rage of human diseases, most notably cancer. Their potential role in matrix degradation during tumor growth originally made them promising targets for the development of new chemotherapy drugs. However, an overall lack of understanding of the roles of specific members of this protease family in cancer pathology resulted in a large number of failed clinical trials and no new MMP drugs entering the market. One of the confounding issues that limited efforts to better define MMP function is the overall large size of the metallo protease family and a lack of highly selective inhibitors for temporally controlled inhibition of specific MMP family members. Furthermore, efforts to genetically knock-out specific proteases have been limited by the essential nature of many of these proteases and the potential for compensation by related family members. Thus, high risk and non-traditional methods to both selectively inhibit and image to dynamics of localization of individual MMP proteases will be required to begin to understand specific functional roles of each MMP family member in the pathogenesis of human diseases such as cancer. This proposal outlines our plans to develop a novel strategy to develop small molecules that can be used to both selectively inhibit and also dynamically image individual MMP proteases in the context of a complex biological system. This method is based on the engineering of specific MMP targets to contain a reactive cysteine residue near the active site that can be used for direct covalent modification by a probe containing a reactive electrophile. Inhibitors that bind to the metal in the active site and have the ability to covalently link to the engineered cysteine residue can then be used to selectively target the Cys-mutant MMPs. This allows selective covalent inhibition and labeling of a single MMP target. At the completion of this project we plan to have the method validated for multiple MMP targets such that it can then be applied to longer term projects designed to further dissect MMP biology. PUBLIC HEALTH RELEVANCE: This project outlines plans to develop a general method to engineer matrix metallo proteases (MMPs) such that they can be selectively inhibited and imaged using small molecule activity based probes. This methodology, once applied to complex in vivo system, will allow studies of the involvement of individual MMP proteases in disease pathology.